Clustering, medium access control, and data aggregation in vehicular ad hoc networks
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2016-03-03
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Universidad de Deusto
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Traffic congestion and traffic accidents are some of the serious problems
faced by humans in their day to day life. These social problems
causes a lot of human inconvenience, traffic congestion for instance
reduces the productivity of humans by wasting a lot of time being on
the road. To reduce the traffic congestion and road accidents, several
traffic efficiency and safety applications can be implemented using
the vehicle to vehicle (V2V) and vehicle to infrastructure (V2I) communication.
The network consisting of vehicles and road side units
(RSUs) are known as vehicular ad hoc networks (VANETs). V2V
and V2I communications exchange two different types of messages,
periodic and event-driven messages. Periodic messages of a vehicle
updates the nearby vehicles about its current position, speed and direction
and event-driven messages are transmitted during a hard brake or
detection of dangerous road condition.
Most of the traffic safety and efficiency applications are based on the
broadcasting of safety or update messages by vehicles or RSUs. This
type of transmission is designed to help reduce road accidents and
traffic congestions. However, during traffic accidents, there can be a
huge number of vehicles in a certain region that can lead to congestion
in the channel access. Furthermore, congestion in the channel also
arises during the busy hours of the day. The reliability of the safety
application depends upon the successful delivery of safety message to
its neighbouring vehicles and RSUs with a predictable delay, which
is one of the main functions of a deterministic medium access control
(MAC) protocol proposed for VANETs.
Another important challenge in VANETs is to achieve scalability. With
the increasing size of the road system, the data load eventually congests
the network channel. This challenge can be solved by reducing the data
collisions and data load through clustering, MAC and data aggregation.
The main aim of this thesis is to design a cluster based MAC protocol
that is scalable in high density scenarios, transmit the safety message
with high reliability, and deliver the safety message with a predictable
delay. Moreover, reduce the channel load during traffic accidents using
data aggregation application.
This thesis makes the following research contributions:
• A cluster head (CH) election, cluster formation, and cluster maintenance
algorithm that increases the stability of the cluster structure
and minimises overall management overhead for the maintenance
of the algorithm.
• A hybrid protocol based on contention free and contention based
channel access. Time division multiple access (TDMA) slot allocation
priority based on different parameters such as future position,
and standard score.
• A DA-CMAC protocol that allocates slots based on the direction
of movement of vehicles.
• A cluster based data aggregation scheme that aggregates data
based on the density of vehicles.
I will show that my CH election protocols, cluster maintenance and
direction aware clustering protocols improves the stability of cluster
architecture, there by reducing the maintenance overhead caused due
to CH re-election, re-clustering, and re-configuration. The CH election
protocols presented here leads to an hierarchical efficient network
topology. Additionally, I will show that the proposed MAC protocols
performs better than the current wireless access for vehicular environment
(WAVE) standard in terms of predictability, reliability, and
scalability. Moreover, the cluster based data aggregation is proposed
to reduce the load in the channel. The protocols are evaluated using
computer simulations that are developed in network simulator ns-2,
and the network simulator ns-3. Moreover, the performance of the
proposed protocols are compared with the WAVE standard, SBCA and
the HCA protocol. Furthermore, the ability of the proposed protocols
are demonstrated by detailed delivery delay analysis, including percentage
of access collisions, cluster and CH lifetime, precision, and
level of aggregation in different densities.
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Matemáticas, Ciencias tecnológicas, Ciencia de los ordenadores, Tecnología de las telecomunicaciones